1. Field of the Invention
The present invention relates to a technique for cooling a battery by blowing air, such as from a cooling fan.
2. Description of the Related Art
Batteries are known to generate Joule heat when being charged or discharged. To prevent an excessive rise in battery temperature due to Joule heat, known battery cooling devices cool batteries by blowing cooling air from a cooling fan.
Japanese Patent Laid-Open Publication No. Hei 8-148190 discloses a battery cooling device for detecting discharge current flowing to a battery supply line by a current sensor, calculating the calorific value of the battery from the detected current value and a pre-stored battery internal resistance value, and supplying cooling air to the battery by controlling a cooling air flow of a cooling fan based on an output in accordance with the calculated calorific value. Furthermore, Japanese Patent Laid-Open Publication No. Hei 8-148190 discloses a battery cooling device for estimating the battery temperature at the end of discharge on the basis of the remaining capacity of the battery and the battery temperature rising rate and controlling the cooling air flow of the cooling fan on the basis of the estimated battery temperature.
Moreover, Japanese Patent Laid-Open Publication No. Hei 9-92347 discloses a battery cooling device for controlling a cooling air flow of a cooling fan on the basis of an estimated internal temperature by estimating the internal temperature of a battery on the basis of the surface temperature of the battery and the calorific value of the battery.
In this manner, the cooling air flow of the cooling fan is controlled on the basis of the battery temperature and calorific value in Japanese Patent Laid-Open Publication No. Hei 8-148190 and Japanese Patent Laid-Open Publication No. Hei 9-92347.
However, the cooling air flow required to cool the battery is influenced not only by parameters indicating the state of the battery, such as battery temperature and calorific value, but also by the surrounding environment of the battery. Namely, the ease of cooling the battery changes depending on the surrounding environment of the battery. Therefore, the cooling air flow of the cooling fan may be excessive or insufficient if the cooling air flow of the cooling fan is determined only by parameters indicating the state of the battery, such as battery temperature and calorific value.